A validated population of male and female monkey breeders (M. nemestrina) contains 86 animals at high or low risk for bad pregnancy outcomes. Such outcomes include abortion, stillbirth, premature birth, low birth weight, and/or neonatal death. Offspring from high risk breeders, low birth weight offspring, and premature newborns exhibit anomalies in growth, feeding behavior, diurnal cycles of basic biological functions, and aspects of learning, social behavior, and motivation. This breeder population is being used as an experimental model to: (1) identify genetic, prenatal, perinatal, and postnatal factors which result in; (2) offspring mortality, prematurity, and mental and social retardation or other disabilities, with the goal of; (3) preventing bad pregnancy outcomes and their associated offspring abnormalities. To approach our goal, we conduct experiments having the following aims: (1) To identify specific factors causing abortions, prevent these abortions, and produce surviving offspring at high risk for developmental abnormalities: (2) To study developmental effects of premature birth by delivering offspring from high and low risk parents at early gestational ages by using C-section procedures; (3) To study the unique contribution of males to bad pregnancy outcomes and to offspring abnormalities by time mating animals that are of opposite risk for bad pregnancy outcome; (4) To identify the interactive effects of parental risk, prenatal stress, perinatal condition of the newborn, and rearing in enriched versus impoverished environmental conditions; and (5) To assess the effects of newborn condition on maternal behavior and mother-infant interactions during the neonatal and early infancy periods. Our final aim: (6) is to relate serological, immunological, infection, fertility, endocrine, brain pathology, and chromosomal findings to offspring abnormalities occurring in all experiments.